What Does Hermetically Sealed Mean? A Guide to Hermetic Sealing

Hermetically sealed means that an enclosure is designed to prevent air, moisture, gases, liquids, and contaminants from passing into or out of it. In aerospace, medical device, semiconductor, and other high-reliability applications, hermetic seals protect sensitive components from environmental exposure and help maintain long-term performance. Depending on the materials and application requirements, these seals may be created through processes such as laser welding, GTAW, brazing, or glass-to-metal sealing.

Hermetic sealing creates an impermeable barrier, effectively protecting what’s inside from any external influence. A hermetic seal ensures that no gas, moisture, or contaminants can pass through, regardless of the surrounding conditions. This is achieved through precise engineering and materials, often using processes such as welding, brazing, or advanced adhesives.

The goal of hermetic sealing is to provide a lasting, airtight enclosure that can withstand extreme conditions—be it high pressure, temperature fluctuations, or exposure to corrosive elements.

To achieve an airtight seal, several methods and materials are used. Here are the most common ones:

Welding

Welding is a highly reliable method for hermetic sealing, especially in industries like aerospace and medical devices. Techniques like TIG welding, GTAW, and laser welding for hermetic sealing help metals fuse together to create a strong, airtight bond. Welding is ideal for applications that require strength, repeatability, and long-term reliability.

Brazing

Brazing is similar to welding but uses a filler metal that melts at a lower temperature than the base metals. This creates a strong bond without melting the core materials, often used in electronics and industrial applications where precision is essential.

Glass-to-Metal Sealing

In some cases, especially in electronics, hermetic seals are created by bonding glass to metal. The differing thermal properties of glass and metal allow for an airtight seal when carefully heated and cooled. This method is common in the production of vacuum tubes, sensors, and medical equipment.

Advanced Adhesives

For less extreme environments, adhesives can be used to form hermetic seals. These advanced adhesives are specially formulated to create impermeable barriers against moisture and gases, often used in consumer electronics and certain medical applications

Although “hermetic” and “airtight” are sometimes used interchangeably, they do not always mean the same thing. Airtight is a general term describing an enclosure that limits the movement of air. A hermetic seal is engineered to control the passage of gases, moisture, liquids, and contaminants according to defined performance requirements.

For critical applications, hermeticity is evaluated against a specified allowable leak rate rather than assumed from appearance alone. The required level of protection depends on factors such as the component, operating environment, pressure, temperature, materials, and expected service life. Aerospace, medical, semiconductor, and electronic components often require more precisely controlled and verified seals than ordinary airtight products.

Hermetic sealing is used when environmental exposure could damage a component, interfere with performance, or shorten its operating life. These seals help protect sensitive assemblies from moisture, oxygen, dust, corrosive substances, pressure changes, and other outside conditions.

Common applications include:

• Electronic packages and enclosures
• Sensors, relays, connectors, and feedthroughs
• Aerospace and defense components
• Medical device housings and assemblies
• Semiconductor equipment and components
• Battery and energy-system enclosures
• Vacuum or controlled-atmosphere assemblies
• Optical and telecommunications components

The appropriate sealing method depends on the component’s materials, geometry, production requirements, operating conditions, and applicable specifications. Welding is often selected for metal assemblies that require a strong, repeatable, and durable seal.

Laser welding is well suited for many metal hermetic-sealing applications because it delivers concentrated energy to a precisely controlled area. This can produce a narrow fusion seam with limited heat input, a relatively small heat-affected zone, and less distortion than many conventional joining processes.

The process is particularly useful for small components, thin-wall enclosures, sensors, electronic packages, medical device assemblies, and other parts that require accurate weld placement. Laser welding can also be automated, helping manufacturers achieve repeatable weld quality across production quantities.

Successful hermetic laser welding still requires proper material selection, joint design, fit-up, cleanliness, tooling, and process control. Joining Technologies provides precision laser welding for critical metal components and can help evaluate the welding requirements for aerospace, medical, defense, semiconductor, energy, and other demanding applications.

Hermetic sealing is essential in a wide range of industries, where protecting components from environmental exposure can be the difference between success and failure. Here are some of the most significant reasons why hermetic sealing is important:

Preventing Contamination

In industries like pharmaceuticals, food packaging, and medical devices, contamination can have devastating effects. Hermetic sealing ensures that no contaminants such as dust, moisture, or microbes can enter the enclosure, maintaining sterility and preserving product integrity.

Enhancing Durability

Hermetic seals protect components from environmental wear and tear, extending the lifespan of the products they enclose. In harsh environments, such as in the aerospace industry or underwater exploration, a hermetic seal ensures that sensitive systems can withstand extreme conditions.

Ensuring Safety

In certain applications, a leak can be catastrophic. For example, in aerospace fuel systems, even a small breach in a seal could lead to dangerous leaks, risking the entire system. Hermetic seals ensure that gases and liquids stay contained, reducing the risk of accidents and ensuring the safety of both equipment and personnel.

Improving Performance of Electronic Components

Electronic devices, especially those used in critical fields like telecommunications, aerospace, and military applications, rely on hermetic sealing to function properly. Exposure to humidity, air, or corrosive gases can degrade the performance of sensitive electronics. Hermetic enclosures keep these elements out, ensuring that circuits, sensors, and other components continue to operate reliably.

Enabling Space Exploration

In space exploration, where equipment must endure the vacuum of space, drastic temperature swings, and cosmic radiation, hermetic sealing is non-negotiable. Every system aboard a spacecraft, from its fuel tanks to its communication devices, relies on airtight seals to function in these extreme environments.

In conclusion, hermetic sealing is crucial for protecting sensitive components in industries ranging from aerospace to electronics. By ensuring airtight protection against environmental factors, it enhances durability, safety, and performance. At Joining Technologies, we offer advanced hermetic sealing solutions, primarily using laser welding to meet the demanding needs of our clients. Our expertise ensures that your systems remain secure and reliable, even in the most challenging environments.